Wicking apparatus for liquid droplet spray device

ABSTRACT

This wicking apparatus includes a liquid reservoir, a wick holder, and a wick. 
     The wick holder has a top part for fitting on the reservoir neck and a bottom part for insertion into the reservoir opening, the top part being plate-formed with a central opening, and with two peripheral projections that are spaced apart and that extend downward from the plate towards the reservoir body, projections for contacting inner and outer walls of the reservoir neck, and a second projection for contacting an outer wall of the reservoir neck, the bottom part having wick supporting arms that extend downwards and have flexible end portions projecting inwardly towards the centre of the reservoir opening. The wick is step-shaped with a larger diameter part, and a smaller diameter part; the interface between them defines a shoulder which is supported and held in place by the flexible end portions of the supporting arms.

The present invention relates to the atomization of liquids in a liquiddroplet dispensing device, and more specifically to a wicking apparatusfor such a device. Such droplet dispensing devices are also sometimescalled atomizers, nebulizers and the like. They normally contain anozzle body on a support part, in particular, a nozzle body of a liquiddroplet spray device which dispenses a liquid substance as a liquiddroplet spray from the device through the nozzles of the nozzle body.They further consist of an actuator based on a vibrating element whichgenerally causes the liquid to vibrate, to be accelerated and expelledas droplets. They further consist of elements such as liquid space,liquid feed and fluid interface to a reservoir, a reservoir as well aselectrical connections between the vibrating element and a correspondingelectronic circuitry.

Such elements may be contained in the aforementioned support part, in afurther support part or they may be contained in a number of supportparts. The liquid may be for example an ambient fragrance, a perfume, aninsecticide, a liquid pharmaceutical formulation, aqueous based liquidsand flammable or combustible liquids.

Such nozzle bodies are sometimes called aperture plates, nozzle arrays,dosing apertures, orifice plates, vibratable membrane members, dosingaperture arrangements, aerosol generators and the like. These terms arehence to be understood as being interchangeable throughout the presentdocument.

Such nozzle bodies and droplet spray devices are well known as such. Forexample, the document WO2007/062698, in the name of the presentApplicant, describes a liquid droplet spray device having a topsubstrate formed of a main body and of a nozzle body. The nozzle bodycontains a nozzle array of liquid droplet outlet means allowing a liquidsubstance contained in the liquid droplet spray device to exit thedevice, in this case as a spray of droplets. Liquid may be supplied froma replaceable reservoir by way of a wick using capillary flow.Generally, the reservoir is a dispensable refill that needs to bereplaced regularly.

The document U.S. Pat. No. 7,017,829 describes a liquid droplet spraydevice having a wicking apparatus with a wick for use in a replaceablereservoir assembly that contains liquid to be atomized by a vibratoryaperture plate configured to dispense the liquid from the reservoirassembly through the orifices of the vibratory plate. In this device,the wick must contact the vibratory plate to allow for capillary flow ofliquid from the reservoir to the plate for ejection of the liquid.

Thus, in order to ensure capillary flow, typically, the wick is toolong, so that any fabrication tolerance, which might lead to a wick thatwould be too short, will be overcompensated.

Furthermore, in order to obtain an acceptable draining ratio of thereservoir, the wick should fully contact the inner bottom surface of thereservoir for it to be capable to substantially drain and empty thereservoir. Indeed, if the wick does not reach the plate, no spray can begenerated or ejected.

To ensure such contact, again, the wick is typically over-sized so as tocompensate for manufacturing tolerances.

However, when a wick that is too long than actually designed is insertedinto the reservoir, and positioned below the orifice plate, the wickwill inevitably be compressed against the plate and against the innerbottom surface of the reservoir. This compression of the wick then leadsto unreliable priming and irregular ejection of liquid each time areservoir is changed.

In fact, by compressing the wick, which is thus forced into contact tothe plate, a so-called squeezing effect is obtained which leads to anincreased flow rate of liquid when the wick is first inserted into areplacement reservoir. However, after a certain moment in time, as shownby curve a in FIG. 1, the wick and plate assembly will stabilize in thenew position and the flow rate will drop from the increased rate to theintended rate.

Clearly, this is highly undesirable for a consumer, as s/he will have toadjust and re-adjust the flow rate each time the reservoir is replacedin order to have a constant flow rate over time.

Document WO 2005/097349 describes a similar liquid droplet spray devicewith a wicking apparatus. The wick is formed of two different materialswith a rigid main section and a compliant top section. The top compliantsection is thus compressible and is pressed into contact with thevibratory orifice plate to allow liquid to flow from the reservoir tothe plate by capillary action, and may then be expelled.

Thus, again, the wick is compressed against the plate thus resulting ina squeezing effect, albeit more moderate as compared with the previousdocument mentioned above, so that here too, an unstable flow rate willoccur when inserting a new reservoir.

As for the draining ratio, in this device the rigid main section of thewick would also have to be longer than designed to compensate formanufacturing tolerances and to ensure a full contact with the innerbottom surface of the reservoir.

It is also known to use wick holders so as to correctly and/or securelyfix a wick in a reservoir. For example, the document U.S. Pat. No.6,896,196 describes a liquid droplet spray device with a wickingapparatus that has a wick holder 8 for receiving a wick. The holder ispositioned onto a reservoir's bottleneck, and holds the wick in place byway of clamping fingers so as to allow for easy insertion of the wickinto the reservoir, while at the same time preventing accidental removalof the wick. However, this document is silent about flow rate ordraining ratios.

In view of the above, it is an object of the present invention toprovide an innovative wicking apparatus for a droplet spray device thatovercomes the inconveniences presented by the prior art documents.

Further, the proposed wicking apparatus can ensure a constant flow rateeven after replacing the reservoir as shown by curve b in FIG. 1, whileat the same time allowing for a high draining ratio despite existingmanufacturing tolerances of wicks.

Thus, the present invention concerns a wicking apparatus as defined inthe appended claims.

Thanks to the construction of the innovative and inventive wickingapparatus according to the present invention an efficient devicefulfilling these objectives may be obtained in a relatively simple andinexpensive manner.

Other features and advantages of the wicking apparatus according to thepresent invention will become clear from reading the followingdescription, which is given solely by way of a non-limitative examplethereby referring to the attached drawings in which:

FIG. 1, already mentioned, shows a schematic representation of flow rateversus time in view of a squeezing effect by curve a in conventionaldevices and by curve b in view of the present invention,

FIG. 2 show an example of the wicking apparatus according to the presentinvention,

FIG. 3 shows a detailed top-side view of the wick holder shown in FIG.2,

FIG. 4 shows a detailed side view of the wick holder shown in FIG. 2,

FIG. 5 shows an example of another reservoir for the wicking apparatusaccording to the present invention,

FIG. 6 shows an example of an alternative wick in the wicking apparatusaccording to the present invention,

FIG. 7 sows an example of a liquid droplet spray device to which awicking apparatus according to the preset invention may be mounted, and

FIG. 8 shows another example of a liquid droplet spray device to which awicking apparatus according to the preset invention may be mounted.

A preferred embodiment will now be described.

FIG. 2 shows an example of the wicking apparatus according to thepresent invention. The wicking apparatus comprises a reservoir 1, a wickholder 2 and a wick 3. FIG. 2 a shows a general view of the wickingapparatus, whereas FIG. 2 b shows a top view thereof. FIG. 2 c shows across-sectional view along lines A-A of FIG. 2 a, and FIG. 2 d shows adetailed view of section B of FIG. 2 c.

As can be seen in these figures, reservoir 1 has, in this example, ageneral bottle shape, with a main body 1 a, and a bottle neck 1 b. Wickholder 2 is fitted over the bottleneck 1 b, and rests thus thereon. Awick 3 is fitted into the wick holder and enters the reservoir tocomplete the device according to the present invention. Wick 3 extendsbeyond the top surface of wick holder so as to enter into capillarycontact with a liquid receiving means of a liquid droplet spray deviceso as to allow for ejection of the liquid as a spray of droplets. Aswill be understood from the following description, this contact ispurely a capillary contact, thus avoiding any compression of wick 3 andthus avoiding the so-called squeezing effect which deteriorates stablefunctioning of prior art devices when an empty reservoir is replaced bya new full one.

Instead of a bottle shape, reservoir 1 may also be a bag-like reservoir,as shown for example in FIG. 5. Such bag-like reservoir can also be acollapsible bag, as is well known in the art.

Thus, in general, reservoir 1 has a reservoir body 1 a for containingthe volatile substance, and a reservoir neck 1 b extending from thereservoir body and terminating in a reservoir opening 1 c (see FIG. 2D)into which a wick holder and a wick may be inserted.

As shown in detail in FIG. 2 d, wick holder 2 has a top part 8 forfitting over reservoir neck 1 b, similar to a bottle cap, and a bottompart 10 for insertion into the reservoir opening. Top part 8 isgenerally flat and plate-formed with a central opening 6 for receiving awick. At the peripheral edge of top part 8, two projections 8 a, 8 b areprovided which are spaced apart and which extend downward from the platetowards reservoir body 1 a when wick holder 2 is fitted onto reservoir1. In this example, these projections follow substantially the entireperiphery of top part 8.

First projection 8 a is arranged on an inner periphery with respect tothe edge of top part 8, and is arranged to contact an inner wall ofreservoir neck 1 b. Second projection 8 b substantially follows the edgeof top part 8 in this example, and is arranged to contact an outer wallof reservoir neck 1 b. In this way, top part 8 sits on the reservoirsupported by reservoir neck 1 b and held in place by first and secondprojections 8 a, 8 b which pinch together reservoir neck 1 b.

This arrangement allows for a precise fitting of wick holder 2 onreservoir 1, as the top of reservoir neck constitutes a referencesurface.

By using a material for wick holder 2 that can be manufactured with highprecision, for example by using a plastic that can be injection-moulded,distances with respect to this reference point can be clearly andaccurately defined.

As shown in FIG. 3, elastic detachment means 12 may be provided on aside surface of second projection 8 b to allow for secure attachment toreservoir neck 1 b and for easy removal there from. Such means are wellknown as such in the art and will not be discussed in more detail here.

FIG. 4 shows a detailed side view of the wick holder shown in FIG. 2. Ascan be seen in this figure, first projection 8 a interfaces withintegrally formed bottom part 10 that continues further downwards by wayof a plurality of wick supporting arms 10 a spaced apart along the inneredge periphery of first projection 8 a. These supporting arms 10 aextend further downwards away from top part 8 and each have a flexibleend portion 10 b projecting inwardly towards the centre of the reservoiropening. These flexible end portions are arranged to allow for a slightvertical displacement by deformation, as will be explained in moredetail further on.

As shown in FIG. 2 d and FIG. 6, wick 3 is step-shaped having a largerdiameter upper part 3 a for supplying by capillary contact liquid to theliquid receiving section of a liquid droplet spray device when mountedthereto, and a smaller diameter lower part 3 b, as compared to thelarger diameter upper part 3 a, for extending into the reservoir 1 tocontact the inner bottom surface thereof when inserted. As can be seenin FIG. 2 d, the interface between larger diameter upper part 3 a andsmaller diameter lower part 3 b defines a shoulder 3 c. When wick 3 isinserted into wick holder 2, his shoulder is supported and held in placeby the flexible end portions 10 b of one or more supporting arms 10 a ofwick holder 8.

Flexible end portions 10 b can slightly move downwards when a certainweight or pressure is applied thereto. This displacement is larger thanthe typical fabrication tolerance of a wick. Generally, a wick can befabricated with a tolerance of its length of around ±0.4 mm. Thedisplacement of the flexible end portion is then chosen, for example, tobe 1 mm to allow to fully absorb the manufacturing tolerances. Thus, forexample, if a wick is supposed to be 12.7 mm long, in reality it may bebetween 12.3 and 13.1 mm. A conventional wicking apparatus would thenhave a wick manufactured with a specified length of at least 13.1 mm, soas to be certain that the wick will be long enough to reach both thebottom inner surface of the reservoir, and to touch the liquid receivingsection for inputting the liquid into the spray device.

Thus, typically such a conventional wicking apparatus will use a wickthat is too long, and will thus compress the wick into place.

However, according to the present invention, a wick is specified formanufacturing for the correct designed length of 12.7 mm. Such wick willnot be compressed, but instead, the flexible end portions 10 b will movedownwards to compensate for any excess length due to manufacturingtolerances.

In fact, the flexible end portions are arranged at a distance such thateven a wick with a minimum length of, in this example, 12.7−0.4=12.3 mmwill arrive at the correct level above wick holder 2 so as to ensure acapillary contact with the liquid receiving section of a spray device.Any longer wick will cause the flexible end portions to lower so as toabsorb the excess length, so that the wick will always arrive at thecorrect level above wick holder 2 so as to ensure a purely capillarycontact with the liquid receiving section of a spray device, free fromcompression, and thus free from any squeezing effect. If, due totolerances, the wick is too short, the flexible end portion 10 b willalso compensate such that the wick will always arrive at the correctlevel above the wick holder.

FIG. 6 shows an example of an alternative wick in the wicking apparatusaccording to the present invention. In this alternative arrangement,wick 13 also is step-shaped having a larger diameter upper part 13 a forsupplying by capillary contact liquid to the liquid receiving section ofa liquid droplet spray device when mounted thereto, and a smallerdiameter lower part 13 b, as compared to the larger diameter upper part3 a, for extending into the reservoir 1 to contact the inner bottomsurface thereof when inserted. Again, the interface between largerdiameter upper part 13 a and smaller diameter lower part 13 b defines ashoulder 13 c. However, these two parts 13 a, 13 b are two separateparts, instead of being formed integrally as described above. Largerdiameter upper part 13 a has a central hole 13 d for receiving smallerdiameter lower part 13 b therein in a slideable manner. S such, thelength of wick 13 may vary, and any fabrication tolerances can also beabsorbed by the inner relative displacement of smaller diameter lowerpart 13 b with respect larger diameter upper part 13 a.

By combining such a wick 13, with the wick holder 2 described above, anymanufacturing tolerance can be compensated for, by the flexible endportions, by the relative displacement of the wick portions, or by acombination of these two.

FIG. 7 sows an example of a liquid droplet spray device to which awicking apparatus according to the preset invention may be mounted. Ascan be seen, liquid droplet spray device 20 comprises a top package 21,a bottom package 22, liquid outlet means 23, and liquid inlet means 24.More details of this device are described in above-mentioned documentWO2007/062698 in the name of the present Applicant Actuating means, suchas a piezoelectric vibrating means, not shown, are provided to actuateany liquid present in the liquid outlet means. Liquid outlet meanscomprises a nozzle array for allowing liquid to exit the spray deviceonce excited. By mounting the wicking apparatus according to the presentinvention, wick 3, 13 will contact the liquid receiving section ofliquid inlet means 24 to allow liquid to enter the spray device bycapillary action only. Once the liquid enters the spray device, it istransported to the liquid outlet means 23. Here, the liquid undergoes avibration, by way of the actuating means, not shown, to excite theliquid so as to expel it through outlet nozzles provide din the outletmeans to generate a spray of droplets.

Thanks to the present invention, the wick will always be correctlypositioned in the liquid receiving means, and will have a capillarycontact therewith that is free from compression, despite anymanufacturing tolerances of the wick length. This ensures a stable flowrate (curve b in FIG. 1).

FIG. 8 shows another example of a liquid droplet spray device to which awicking apparatus according to the present invention may be mounted. Inthis spray device, the liquid outlet means take the form of a vibratorydome-shaped nozzle plate, which may be similar to above-mentioneddocument U.S. Pat. No. 7,017,829. Thus, the liquid inlet means 31 arearranged centrically below the liquid outlet means 34 in that the wicktransports the liquid to the bottom of the vibratory plate, which isthen excited by suitable vibrating means, for example, circularvibrating element 32 to suck in the liquid into the nozzles of thenozzle plate 31 and to expel the liquid as a spray of droplets throughliquid outlet means 34.

Having described now the preferred embodiment of this invention, it willbe apparent to one of skill in the art that other embodimentsincorporating its concept may be used. It is felt, therefore, that thisinvention should not be limited to the disclosed embodiment, but rathershould be limited only by the scope of the appended claims.

1. Wicking apparatus for volatile substances that may be ejected as aspray of droplets by a liquid droplet spray device when fitted with thewicking apparatus, the wicking apparatus comprising: a volatilesubstance reservoir, a wick holder, and a wick; the reservoir having areservoir body for containing the volatile substance, and a reservoirneck extending from the reservoir body and terminating in a reservoiropening into which a wick holder and a wick may be inserted; the wickholder having a top part for fitting on the reservoir neck and a bottompart for insertion into the reservoir opening, the top part being in theform of a plate with a central opening for receiving a wick, and withtwo peripheral projections that are spaced apart and that extenddownward from the plate towards the reservoir body when fitted on thereservoir along substantially the entire periphery of the top part, afirst projection of the two projections for contacting an inner wall ofthe reservoir neck, and a second projection of the two projections forcontacting an outer wall of the reservoir neck, so that the top partsits on the reservoir supported by the reservoir neck and held in placeby the first and second projections, the bottom part being integrallyformed with the first projection and having a plurality of wicksupporting arms spaced apart along its periphery, the supporting armsextending further downwards away from said top part and having flexibleend portions projecting inwardly towards a centre of the reservoiropening; the wick being step-shaped having a larger diameter part forsupplying by capillary contact liquid to a liquid receiving section ofthe liquid droplet spray device when mounted thereto, and a smallerdiameter part, as compared to the larger diameter part, for extendinginto the reservoir to contact an inner bottom surface thereof wheninserted, the interface between the larger diameter part and the smallerdiameter part defining a shoulder which is supported and held in placeby the flexible end portions of the plurality of supporting arms. 2.Wicking apparatus according to claim 1, wherein said reservoir is abottle.
 3. Wicking apparatus according to claim 1, wherein saidreservoir is a collapsible bag.
 4. Wicking apparatus according to anyoneof claim 1, wherein said wick comprises two separate parts, said largerdiameter part having a central opening, and said smaller diameter partbeing slideably fitted into said larger diameter part.
 5. Liquid dropletspray device comprising a nozzle body, a piezo-electric actuator, afluid chamber located below said nozzle body, and a liquid receivingsection, and a wicking apparatus according to claim 1, wherein saidliquid receiving section is arranged to receive a liquid throughcapillary contact from said wick, and to provide said fluid chamber withsaid liquid for ejecting said received liquid as a spray of droplets. 6.Liquid droplet spray device according to claim 5, wherein said liquidreceiving section is arranged eccentric with respect to said nozzlebody.
 7. Liquid droplet spray device according to claim 5, wherein saidliquid receiving section is arranged centric with respect to said nozzlebody.
 8. Liquid droplet spray device according to claim 7, wherein saidnozzle body is a vibratory plate.